Three weeks have passed since an Exxon Mobil pipeline burst, sending 1,000 barrels of oil into the Yellowstone River, and now the incident has brought to light some startling facts. For instance, federal officials really have no idea how many pipelines are buried under our rivers or how far below the ground they sit, which means that they are pretty much clueless about where pipes are carrying hazardous liquids under our waterways. Wonderful. Fearing that another spill is imminent, regulators are scrambling to find out which lines might be in danger, and lawmakers — from both the left and the right — are raising red flags, calling for the need for government regulation in what has been largely a self-regulated industry.

“If we don’t know where the (pipelines) are in the ground and how many crossings are under rivers and streams so we can check on them, we’re asking for another catastrophe,” said U.S. Sen. Jon Tester to the Associated Press. The U.S. Pipeline and Hazardous Material Safety Administration could not immediately provide an inventory of pipeline crossings when Tester requested the information.

Pipeline officials told the Associated Press that there is an estimate of 35,000 river, stream and lake crossings within the country’s half-million-mile network of natural gas and hazardous liquid transmission pipelines. The official also said that a review of pipeline crossings in the Missouri River basin in Montana and Wyoming is under way, and they have plans to expand that effort nationwide. The fact that it is not already a nationwide review is a bit unsettling, but not surprising.

U.S. rivers have experienced high and fast moving waters this year, which can scour river bottoms and lead to the exposure of pipelines. This is the theory that’s been put forth about the Exxon line, but the investigation is still underway. The federal government requires pipes to be buried at least four feet underground, but if the ground is rocky, it can be less. Pipeline companies are never required to reevaluate the original depth.

Violent river flows and concerns over the Yellowstone’s banks eroding caused Exxon to evaluate the pipeline prior to the July 1st failure, but the company decided to not shut it down — even though a natural gas company with a neighboring line shut down theirs. Exxon has acknowledged this was a mistake, but it just goes to show what more stringent regulations could have prevented.